Solenoidal superconducting magnet structure

ABSTRACT

A method of manufacturing a solenoidal magnet structure, includes the step of providing a collapsible accurate mold in which to wind the coils winding wire into defined positions in the mold, placing a mechanical support structure over the coils so wound, impregnating the coils and the mechanical support structure with a thermosetting resin, allowing the thermosetting resin to harden, and collapsing the mold and removing the resultant solenoidal magnet structure formed by the resin impregnated coils and the mechanical support structure from the mold as a single solid piece.

RELATED APPLICATION

The present application is a divisional of application Ser. No.11/734,915, filed Apr. 13, 2007 now U.S. Pat. No. 7,849,587.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacture of solenoidalmagnet coils, and to solenoidal magnet coils themselves. In particular,it relates to such coils for generating high strength magnetic fields,which may be applied in systems such as nuclear magnetic resonance (NMR)or magnetic resonance imaging (MRI).

2. Description of the Prior Art

FIGS. 1A-1B illustrate cross-sectional and axial sectional views,respectively, of a conventional solenoidal magnet arrangement for anuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI)system. A number of coils of superconducting wire are wound onto aformer 1. The resulting assembly is housed inside a cryogen vessel 2which is at least partly filled with a liquid cryogen 2 a at its boilingpoint. The coils are thereby held at a temperature below their criticalpoint.

The former 1 is typically constructed of aluminum, which is machined toensure accurate dimensions of the former 1, in turn ensuring accuratesize and position of the coils which are wound onto the former. Suchaccuracy is essential in ensuring the homogeneity and reliability of theresultant magnetic field. Superconducting magnets may quench due to evena small amount of movement of even one turn of the coil. The formersmust therefore be very rigid. These requirements combine to render theproduction of formers very expensive.

Also illustrated in FIGS. 1A-1B are an outer vacuum container 4 andthermal shields 3. As is well known, these serve to thermally isolatethe cryogen tank from the surrounding atmosphere. Insulation 5 may beplaced inside the space between the outer vacuum container and thethermal shield. However, as can be seen in FIGS. 1A-1B, these elementsalso reduce the available inside diameter 4 a of the solenoidal magnet.Since the inside diameter 4 a of the solenoidal magnet is required to beof a certain dimension to allow patient access, the presence of theouter vacuum container 4 and the thermal shields 3 effectively increasesthe diameter of the magnet coils and the former 1, adding to the cost ofthe overall arrangement.

The cost of producing a former 1 such as illustrated in FIGS. 1A-1B anddescribed above is accounted for approximately equally by labor costsand material costs. Among other objectives, the present invention seeksto reduce the labor costs involved in producing a solenoidal magnetstructure.

U.S. Pat. No. 5,917,393 describes a solenoidal superconducting magnetarrangement wherein the various coils are mounted on an inner or outersurface of a thermally conductive cylindrical former, whereby coolingmay be applied through the material of the former. The coils arethermally connected to, but electrically isolated from, the material ofthe cylindrical former.

SUMMARY OF THE INVENTION

An object of the present invention is to alleviate at least some of theproblems of the prior art described above, and to provide a relativelyinexpensive and lightweight former which is capable of withstanding theforces applied to it in use, so that the former provides accurate andstable positioning of the coils of the solenoidal magnet.

The above object is achieved in accordance with a first embodiment ofthe invention by a method for manufacturing a solenoidal magnetstructure including the steps of providing a collapsible mold in whichto wind the coils, winding wire into predefined positions in the mold,placing a mechanical support structure over the coils that have beenwound in the mold, impregnating the coils and the mechanical supportstructure with a thermosetting resin, allowing the thermosetting resinto harden, and collapsing the mold and removing the resulting solenoidalmagnet structure, that includes the resin-impregnated coils and themechanical structure from the mold, as a single solid piece.

The above object also is achieved in accordance with the presentinvention in a second embodiment of a method for manufacturing a magnetstructure, that includes the steps of providing a collapsible mold inwhich to wind the coils, placing a mechanical support structure intodefined positions in the mold, winding the wire over the mechanicalsupport structure that has been placed in the mold, impregnating thecoils and the mechanical support structure with a thermosetting resin,allowing the thermosetting resin to harden, and collapsing the mold andremoving the resulting solenoidal magnet structure, including theresin-impregnated coils and the mechanical support structure, from themold as a single solid piece.

The object also is achieved in accordance with the present invention bya solenoidal magnet structure having a wire wound into coils, and amagnetic support structure located over the wound coils, with theentirety of the coils and the mechanical support structure beingmonolithically impregnated with a thermosetting resin.

The above object also is achieved in accordance with the presentinvention by a solenoidal magnet structure having a magnet supportstructure, and a wire wound into coils over the mechanical supportstructure, with the entirety of the magnetic support structure and thecoils being monolithically impregnated with a thermosetting resin.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B show a solenoidal magnet structure housed within a cryostat,according to the prior art.

FIG. 2 shows an overall perspective view of an assembly of coils andstaves according to an embodiment of the present invention.

FIG. 3 shows an axial view of an assembly of coils and staves accordingto an embodiment of the present invention.

FIGS. 3A and 3B show a straight stave and a shaped stave, respectivelyfor use in accordance with the invention.

FIG. 4 shows an arrangement for retaining outer coils coaxially withinner coils.

FIG. 5 shows a cross-section through a stave which has a cooling channelpassing therethrough.

FIG. 6 illustrates a mold suitable for mold impregnated coils accordingto an embodiment of the present invention.

FIG. 7 shows an arrangement for assembling coils onto their supportstaves.

FIGS. 8A-8D show steps in a method for producing an inner former for theGRP concept.

FIG. 9 shows a cooling loop refrigeration arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows an overall perspective view of an assembly of coils 20 andstaves 22 according to an embodiment of the present invention. The coilsare divided into inner coils 20 a and outer coils 20 b.

FIG. 3 shows an axial view of an assembly of coils 20 and staves 22according to an embodiment of the present invention. In FIG. 3, staves22 are shown only partially surrounding the inner coils 20 a. However,it should be understood that the staves are present around the entireperimeter of the inner coils 20 a in the embodiment illustrated. Thestaves 22 need not be contiguous around the entire perimeter of thecoils 20 a, as illustrated, but may be symmetrically spaced atintervals. However, the staves 22 should be sufficient in number andstrength to ensure that the coils 20 are accurately and rigidlypositioned, sufficiently to withstand the forces placed on the coils.

Outer coils 20 b are retained in a coaxial alignment with inner coils 20a. FIG. 4 illustrates one example arrangement for achieving this. Innercoils 20 a are retained in their correct relative position by staves 22.Outer coils 20 b are similarly held in their correct relative positionsby staves 22. In order to minimize the overall dimension of thesolenoidal magnet assembly, the staves 22 may be placed on the outercircumference of the inner coils 20 a and on the inner circumference ofthe outer coils 20 b. However, the staves 22 may be placed on the outeror inner circumference of any of the coils, as may be preferred for anyreason. In order to retain the inner and outer coils in the requiredrelative positions, webs 24 are connected between corresponding staves22 of the inner and outer sets of coils. As shown in FIG. 4, these webs24 may take the form of plates of solid material such as aluminum orglass reinforced plastic (GRP) attached between the staves 22. Tofacilitate attachment of such webs, the staves 22 may be manufacturedwith fixing lugs 26. Fixing holes may then be drilled through the fixinglugs at appropriate points, and the webs attached by bolts or similarfastening means 28 passing through the fixing lugs. Alternatively,mechanical clamps may be provided and arranged to clamp the webs 24 tothe fixing lugs 26. Mechanical clamps may alternatively be provided toclamp the webs 24 directly to the body of the staves 22, obviating thenecessity for fixing lugs 26.

As illustrated in FIG. 2, a solenoidal magnet according to the presentinvention may be arranged such that the inner coils 20 a may be oflesser diameter than in the case of a prior art arrangement such asshown in FIGS. 1A-1B. This is because the prior art arrangement of FIGS.1A-1B relies on compressive strength of the former 1 to support thecoils in operation. As a result of this, the former 1 must be presentwithin the inner diameter of the inner coils, which has either theeffect of reducing the inner diameter 4 a available for accommodating apatient, or increasing the dimension of the inner coils, in turnincreasing the cost of the coils and so also the magnet assembly as awhole.

Solenoidal magnet structures according to the present invention may becooled by immersion in a cryogen vessel, similarly to the prior artarrangement illustrated in FIGS. 1A-1B. Alternatively, cooling may beeffected by providing hollow staves 22, and causing a cryogen tocirculate within the staves. In such embodiments, the coils 20 must bein effective thermal contact with the cooled staves 22, and the wholeshould be adequately isolated from ambient temperature to allow thesuperconducting switches and other components requiring an isothermalsurface could be mounted on the staves. By providing cooling through thestaves, then it is no longer necessary to provide a cryogen vessel suchas illustrated at 2 in FIGS. 1A-1B. This will further reduce the size,weight and cost of the resulting system.

FIG. 5 illustrates a cross-section through a stave 22 which isparticularly suitable in such embodiments. The stave 22 is hollow with acooling channel 30 passing through it. Advantageously, the inner surfaceof the cooling channel includes ribs 32 that increase the inner surfacearea of the cooling channel in contact with the cooling fluid, therebyincreasing the effectiveness of the cooling of the stave. Shield coilsupports and other supports may be extruded into the profile of thestaves.

According to further embodiments of the invention, arrangements may bemade to cool the staves 22, while thermal conduction along the materialof the staves causes cooling of the coils. In such embodiments, thestaves may be cooled by direct refrigeration, or by a cooling loop. FIG.9 schematically illustrates a cooling loop arrangement for causing theliquid cryogen 78 to circulate around the cryogen tubes 79. A relativelysmall cryogen tank 80 is provided in the cryogen tube circuit. Arecondensing refrigerator 82 is also provided. In operation, some of theliquid cryogen 78 in cryogen tube 79 will absorb heat from the cryogentube 79, and thus from the staves 22. This will cause some of the liquidcryogen 78 to boil into a gaseous state. The boiled-off cryogen gas 84will rise toward the top of the cryogen tube circuit, and will enter therecondensing refrigerator 82. The recondensing refrigerator 82 operatesto cool the cryogen gas 84, recondensing it into liquid cryogen 78, andremoving heat from the system. As illustrated in FIG. 9, boiling of theliquid cryogen will take place substantially on the right side of thecircuit as illustrated, and will rise to the recondensing refrigerator82. The recondensed liquid cryogen supplied by refrigerator 82 willdescend through the left hand side of tube 79, as illustrated. Hence,this arrangement provides continuous circulation of the cryogen, andeffective cooling. Although a cryogen tank 80 is required, the volume ofliquid cryogen 78 required is very much reduced as compared to cryogentanks 2 of the prior art, which allowed immersion of the magnet in abath of liquid cryogen.

An advantage of the arrangement of the present invention is that thefrictional interface 34 between coils and former, illustrated at inFIGS. 1A-1B, is eliminated. This frictional interface may provoke quenchin prior art arrangements, since movement of a coil in frictionalcontact with the former may cause sufficient localized heating to bringabout a quench. Since there are no such frictional interfaces in thearrangement of the present invention, such risks are not present. Thebody force, that is the electromagnetic force acting on the coils, isrestrained by the shear bond strength between the coils and the stavesor other mechanical support structure. The coils are manufactured andretained by a mechanical support structure according to any of themethods described elsewhere within the present application, and suchmanner of manufacture provides the required body strength without theneed for formers. The interfacial shear strength required between thecoils and the staves to maintain their position when subjected to theelectromagnetic loads is −3 Mpa, typically 10% of the shear strengthachieved by the bonding method within the coils to prevent movement ofindividual turns, and is therefore within the capability of existingtechnology.

Patient comfort and accessibility of clinicians in MRI systems may bothbe improved by reducing the length of the magnet. Coil arrangementswhich permit this length reduction, while maintaining field quality mayresult in coil body forces which act in an axial direction away from thecenter of the magnet. Conventional methods of restraining these forcesrequire additional former material to be positioned on the end of thecoil increasing the length of the magnet system. By utilizing the shearstrength at the interface between the coils and staves or othermechanical support structure, such additional material can be avoidedand a shorter magnet system length achieved.

The present invention particularly provides a method of manufacturing asolenoidal magnet structure. An embodiment of the present invention willnow be discussed.

Firstly, an accurate mold is required in which to wind the coils.Because no former is to be provided, the accurate dimensions andrelative spacing of the coils are defined by this mold, which mustaccordingly be very accurately made, and of a durable material, to allowa single mold to be used to produce many magnet structures. The mold isarranged to be collapsible. Superconducting wire is wound into definedpositions in the mold. Typically, these positions will be recesses inthe surface of the mold. A mechanical support structure, such as staves22 may be placed over the coils so wound or a composite tube ofreinforced resin may be formed over the coils so wound, by windingreinforcing material over the coils then resin impregnating as discussedbelow. A further mold may be placed over the coils and the mechanicalsupport structure to form an enclosed mold cavity. The coils and themechanical support structure within the mold are monolithicallyimpregnated with a thermosetting resin. This is allowed to harden andthe resin impregnated coils and mechanical support structure are movedfrom the mold as a single solid piece. The impregnation step ispreferably performed in a vacuum, to avoid bubbles of air or other gaswhich might otherwise be trapped in the winding and cause stresses inthe finished piece. FIG. 6 illustrates a suitable mold 40, in moredetail. The mold may be provided with a lining, such as inpolytetrafluoroethylene PTFE, to aid in releasing the finished articles.

A particular advantage of this method of forming the solenoidal coilarrangement is in that the coils are accurately dimensioned andpositioned relative to each other by the shape of the mold. Themechanical support structure that is formed onto the coils does notitself need to be accurately dimensioned, since the positioning of thecoils is defined by the mold, and the mechanical support structuremerely serves to securely retain the coils in their relative positionsas defined by the mold.

This is particularly advantageous since the mold, which must be veryaccurately dimensioned, and is relatively expensive, may be re-usedseveral times to produce a number of similar solenoidal magnetstructures. Conventionally, the mechanical support means itself has beenthe accurately dimensioned, expensive component. Use of the method ofthe present invention, using an accurately machined mold to define thedimensions and relative positions of the coils, accordingly allowsproduction of accurate solenoidal magnet structures for a reduced cost,and in reduced time, as compared to existing methods of production.

In producing solenoidal magnets having inner field coils 20 a (FIG. 2)and outer shield coils 20 b, the relative position of the shield coilsto each other, and the relative position of the field coils to eachother, is more critical than the relative position of the shield coilsto the field coils. The field coils and the shield coils may each beproduced, and mounted on a mechanical support structure, by the methoddescribed above.

FIG. 4 shows a mechanical support structure which may be employed toretain a shield coil 20 b assembly relative to a field coil 20 aassembly. The staves 22 may each have a fixing lug 26 (shown in FIG. 4)provided for this purpose, which is drilled to provide holes for fixingbolts. Alternatively, the holes and bolts may pass through the body ofthe stave 22 itself.

According to an embodiment of the present invention, the staves 22 arepositioned in contact with the coils 20 in a mold prior to theimpregnation step when thermosetting resin is applied to monolithicallyembed the whole assembly to produce a single solid article. Typicallyvacuum impregnation is used. The coils 20 may be attached to staves 22by cloth impregnated with the thermosetting resin. Again, the molds maybe provided with a lining, such as in polytetrafluoroethylene PTFE, toaid in releasing the finished articles.

In some alternative embodiments, a wet lay-up process may be employed,where the resin is applied as a coating on the coil conductor, and aspart of the mechanical support structure, either as a coating on stavesor as an impregnated cloth or similar material.

The staves 22 may be conveniently manufactured as aluminum extrusions,which are relatively inexpensive yet mechanically rigid and thermallyconductive enough for the purposes of the present invention.Alternatively, the staves may be formed from rolled and welded tubes, orfilament-wound tubes.

Typically in solenoidal magnet structures, some coils will be ofdifferent internal or external diameter from others. In this case, itmay be necessary to bring all coils to a common diameter to enable themall to be attached to straight staves. The alternative is to provideshaped staves which correspond to the various diameters of the coils.This option is however presently considered to be uneconomical. FIGS.3A-3B illustrate straight and shaped staves, respectively, useful inthis application. Differences in the relevant diameters of the coils maybe corrected by use of a filler layer of resin-impregnated clothover-wrap, typically employing glass fiber over-wrap. This may be addedwhile the coil is in a mold, being added either as resin impregnatedcloth or dry cloth to be impregnated in the mold.

The coils 20 are wound within corresponding parts of the mold, accordingto the method described above. In the mold, a filler material such asresin impregnated glass fiber may be wound over coils in order to fillthe mold to the top. For example, such filler material may be providedto a depth of 5-10 mm. As illustrated in FIG. 6, the mold may be acollapsible mandrel having at least one removable section 42, allowingthe mold to be disassembled and removed from the interior of the moldedcoils 20.

The use of relatively inaccurate mechanical support structure for thecoils, being staves of aluminum extrusions or tubes, and molded resin isrendered possible by use of accurate tooling. All of the importantrelative positions of features of the solenoidal structure are definedby the molds or other assembly tooling, resulting in a relatively lowunit cost of the solenoidal magnet arrangements produced, while therelatively expensive molds and tooling may be re-used a number of timesto produce several solenoidal magnet coil assemblies.

The final structure may be further strengthened to prevent anysignificant deformation of the staves used.

If refrigeration by cooling loop is employed, then the interposition ofglass filler layers between the coils and the cooling loop, which mayfor example be incorporated within the staves, should be avoided. Thismay be achieved by use of shaped staves such as shown in FIG. 3B, or thesolenoidal coil structure would need to be redesigned to avoid the needfor coils of differing external diameter. While staves may be employedfor the purposes of cooling and mechanical support, is has been foundthat twelve or more staves should be provided for mechanical support,while as few as six staves may prove sufficient for cooling purposes.

In certain preferred embodiments, mechanical supports may be added onthe end coils of an assembly. The end coils suffer the highestmechanical load due to the effects of the generated magnetic field. Suchsupports may be in the form of rolled extrusions or a resin impregnatedglass support ring. These supports may be clamped onto the shield coils.

While the general tendency is to design solenoidal magnets to be asshort as possible, a limit may be reached where the end coils are underrepulsive force, tending to push them away from the body of the magnet.In such cases, mechanical retaining means may be required on the outersurfaces of the coils, which at least partly defeats the lengthreduction obtained by placing the end coils in their position.

The assembly formed by the outer shield coils and their support stavesmay be assembled in the following manner, as illustrated in thecross-section shown in FIG. 7. A former 50 is provided having cavities52 to accommodate at least part of the length of staves 22. The staves22 are placed in the cavities 52 in the former 50, and the coils 20 bare wound onto the former 50, over the staves 22. The coils 20 b areimpregnated and the coils are bonded to the staves in a single processin the manner described for other coils. Struts or webs may be providedto mechanically retain the two assemblies together: the first assemblyincluding field coils held together by staves, and shield coils heldtogether by another set of staves. A suitable arrangement is discussedabove with reference to FIG. 4. In certain embodiments, the staves maybe formed of a reinforcing material, such as glass fiber cloth, which isimpregnated with resin during the described method, to providereinforced resin staves.

FIGS. 8A-8D illustrate several views of steps in a method ofmanufacturing a solenoidal magnet structure according to the presentinvention, wherein the mechanical support structure consists of areinforced resin tube 102. FIGS. 8A and 8B show a partial end-view and apartial axial cross-section, respectively, of a mold filled with coilsand support structure, during the manufacture of a solenoidal magnetcoil assembly according to the present invention, having a reinforcedresin tube mechanical support structure 102. The mold includes an innertube member 80 which retains tool segments 82, 84. The tube 80 may be acomplete cylindrical tube, or may be divided into segments. In use, thetube 80 and tool segments 82, 84 are retained together by detachablemechanical retaining means, such as the bolts 86 illustrated, to form agenerally cylindrical inner surface of the mold.

As shown in FIG. 8B, the tool segments have cavities 88 for retainingcoils 90 as they are wound onto the mold, and cavities 92 for retainingelectrical leads and other service components. Special arrangements maybe made for accommodating the end coils 94. As illustrated, a step 96may be cut into the end of the tool segments 82, 84, and a flat tool endpiece 98 attached to the end of the tube 80 to enclose a cavity to holdend coil 94 as it is wound. A sleeve of filler material 104 is fittedafter winding of the inner coil set and to provide support for thewinding of the end coils.

Over the top of coils 90 and leads and service components 92, a fillermaterial 104 is laid. This filler material 104 is typically glass fibercloth, but may be other types of filler compatible with the resin usedand which has an acceptable thermal coefficient of expansion. A moldouter 100 is provided to surround the tool segments and to define themold cavity 99 with the tool segments 82, 84 and end pieces 98, if any.While the tool segments 82, 84 must be accurately formed and accuratelypositioned, it is not necessary to apply such a degree of accuracy tothe position and shape of the mold outer 100.

As illustrated in FIG. 8B, the mold cavity 99 is defined by the toolsegments 82, 84 and the mold outer 100 and end pieces 98, if any. Themold cavity is open in certain locations 108, e.g. at its ends. Openingsmay also be provided through the mold outer. An impregnation trough 110is affixed around the mold structure, and an impregnation resin isforced through the openings 108 from the impregnation trough into themold, to monolithically impregnate the coils 90, leads and servicecomponents 92, and filler material 104, to produce a single solidarticle, being the solenoidal magnet structure comprising coils and themechanical support structure. Once the assembly has been fullyimpregnated and the resin has set, the various pieces of the mold 82,84, 98, 100 are moved away from the resultant molded structure. Firstly,the impregnation trough 108 and end pieces 98 should be removed from themold. The mold outer 100 may also be removed at this stage, or may beremoved later. Typically, and with reference to FIGS. 8A, 8B, the tube80 is detached from the tool segments. If the tube 80 is in a singlepiece, it can be slid out from the central bore of the assembly. If thetube 80 is split into segments, these segments may be dismantled andremoved from the bore. The tool segments 82, 84 are then removed fromthe molded article. In the example shown in FIG. 8A, the tool segment 82is tapered to narrow away from the bore of the mold. Such segmentsshould be removed first, to provide clearance for removal of theremaining tool segments 84.

FIG. 8C shows an example of a solenoidal coil assembly 111 producedaccording to the method described above. The coils 90 are impregnatedwith resin and have dimensions defined by the accurate surfaces of thetool segments 82, 84. They are bonded by the impregnated resin to amechanical support structure 112 composed of the impregnated resinfilled with filler material. The shear strength of the mechanical bondbetween coils and staves provided by the impregnated resin is equallyeffective in both directions. The coils are accordingly rigidly held inaccurate relative positions by the mechanical support structure. The endcoil 94 is retained by a rather different structure. A thicker fillerlayer 114 is provided, adjacent to the end coil and bonded to it by theimpregnated resin. A further filler layer 116 is provided over theexternal circumference of the end coil, bonded to the end coil by theimpregnated resin.

FIG. 8D shows a partial cross-section of a shield coil arrangementaccording to an embodiment of the present invention. A shield coil 118is impregnated with resin, and bonded by that resin to a mechanicalsupport structure 120. The structure is shown mounted inside a vessel122 provided with a locating element 124.

In variants of the method described in relation to FIGS. 8A-8D, thefiller material 104 and the mold 100 may be arranged such that, ratherthan producing a complete reinforced-resin tube 102, a number ofreinforced resin staves are produced, either on an outer or an innersurface of the coils 90, in an arrangement similar to that illustratedin FIG. 2 or FIG. 7.

While the present invention has been particularly described withreference to solenoidal magnet coils for systems such as nuclearmagnetic resonance (NMR) or magnetic resonance imaging (MRI), it may beapplied to the manufacture of solenoidal magnet coils, and to solenoidalmagnet coils themselves for any application, particularly those in whichprecise coil alignment is required.

Although modifications and changes may be suggested by those skilled inthe art, it is the intention of the inventors to embody within thepatent warranted hereon all changes and modifications as reasonably andproperly come within the scope of their contribution to the art.

1. A solenoidal superconducting magnet structure comprising: asuperconducting wire wound into coils having an outermost exterior; amechanical support structure comprising a reinforced resin tube locatedover said outermost exterior of said coils, said coils and saidmechanical support structure forming an assembly; and thermosettingresin in which an entirety of said assembly is monolithically embeddedand forming, when said thermosetting resin sets a single solid article.2. A solenoidal superconducting magnet structure as claimed in claim 1comprising electrical leads connected to said coils and retained in saidthermosetting resin.
 3. A solenoidal superconducting magnet structure asclaimed in claim 1 wherein said coils comprise a generally cylindricalinner set of coils surrounded by a generally cylindrical outer set ofcoils, and wherein said mechanical reinforced resin tube comprises afirst support structure located over said inner set of coils and asecond reinforced resin tube located over said second set of coils, andfurther support structure components mechanically joining said first andsecond reinforced resin tubes.
 4. A solenoidal superconducting magnetstructure as claimed in claim 1 comprising a plurality ofsuperconducting wires respectively forming different coils withrespectively different diameters, and comprising a filler layer disposedbetween said coils of respectively different diameters and saidreinforced resin tube.
 5. A solenoidal superconducting magnet structureas claimed in claim 4 wherein said filler layer comprises a layer ofresin-impregnated cloth overwrap.
 6. A solenoidal superconducting magnetstructure as claimed in claim 1 comprising an end coil of saidsolenoidal superconducting magnet structure retained to said mechanicalsupport structure by a filler layer adjacent to said end coil and bondedthereto by said resin, and a further filler layer over an externalcircumference of said end coil, bonded to said end coil by said resin.7. A solenoidal superconducting magnet structure comprising: amechanical support structure comprising a reinforced resin tube; atleast one superconducting wire wound into a coil of said solenoidalsuperconducting magnet structure over said mechanical support structure,said mechanical support structure and said at least one coil forming anassembly; and thermosetting resin in which an entirety of said assemblyis monolithically embedded and forming, when said thermosetting resinsets a single solid article.
 8. A solenoidal superconducting magnetstructure as claimed in claim 7 comprising electrical leads connected tosaid coils and retained in said thermosetting resin.
 9. A solenoidalsuperconducting magnet structure as claimed in claim 7 comprising aplurality of wires respectively forming different coils withrespectively different diameters, and comprising a filler layer disposedbetween said coils of respectively different diameters and saidreinforced resin tube.
 10. A solenoidal superconducting magnet structureas claimed in claim 9 wherein said filler layer comprises a layer ofresin-impregnated cloth overwrap overlap.
 11. A solenoidalsuperconducting magnet structure as claimed in claim 7 comprising an endcoil of said solenoidal superconducting magnet structure retained tosaid mechanical support structure by a filler layer adjacent to said endcoil and bonded thereto by said resin, and a further filler layer overan external circumference of said end coil, bonded to said end coil bysaid resin.